Method and equipment for the intensive use of oxygen in open hearth furnaces for the production of steel



Feb. 19, 1963 M. FORESI ETAL 3,078,084

METHOD AND EQUIPMENT FOR THE INTENSIVE USE OF OXYGEN IN OPEN HEARTH FURNACES FOR THE PRODUCTION OF STEEL Filed Oct. 9, 1959 43 T 4 T 43 5E s=- i s: 45 44 i v k Fig.3

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United States Patent @fifice 3,978,084 Patented Feb. 19, 1963 savanna METHUD AND EQUIPMENT FQR TEE? lN'lENfllVE USE OF @XYGFEN EN (WEN HEARTH FUFJ JACES FQR THE PRQDUCTEQN 6F STEEL Mario Foresi, Genoa-Pegli, and Salvatore Ungaro, Genoa, Italy, assignors to Cornigliano Societa Azioni, Genoa, Italy Filed Oct. Q, 1959, Ser. No. 3455M Claims priority, application Italy Nov. 12, 1958 tllaims. (Cl. 266-33) In open hearth furnaces, in the production of steel, it is a known practice to use oxygen which is introduced into the flame or on to the bath with the aim of accelerating the siderurgical process; also known are the difiiculties of suitably subdividing the oxygen between the flame and the bath, and of avoiding dangerous concentrations of heat which reflect themselves in a limitat'on in the employment of the oxygen, in a wearing action on the fireproof bricks, and in a heavy formation of red iron oxide fumes.

The method and equipment in accordance with the present invention successfully permit, simultaneously and in a variable manner, of either the insufi'lation of oxygen in the flame, in a quantity and a position such as are likely to achieve its highest efiiciency in the whole of the operation while at the same time preventing the flame, which is enriched in oxygen, from developing a Wearing action on the refractory bricks, or the sending of a controlled jet of oxygen, at a very high speed, on to the charge, with the aim of activating the thermal exchange between the flame and the charge for the purpose of accelerating the transformation processes of the metal without dangerous concentrations of heat, and for the purpose of completely burning up the reaction gases.

The method for the intensive use of oxygen in an open hearth furnace, for the production of steel, is characterized by the fact that the oxygen is insufflated into the furnace at a very high velocity below the lighted fuel, and the jet of oxygen, in the shape of a cone, is regulated in such a manner that a part of the said jet shall reach the cone of lighted fuel with a view to activatfng the flame, and another part of the jet, which is appropriately distributed for the purpose of preventing a concentration of heat, shall reach the charge so as to act physically and chemically on the charge and on the reaction gases.

The afore-mentioned method is also characterized by the fact that the cone of the lighted fuel, with its bottom portion, comes into contact with the oxygens cone-shaped jet, and the flame reaches a higher temperature whereas, with its upper portion, which is not in contact with the oxygen but with the air originating from the regenerator, it protects the furnaces refractory lining from the high temperature reached by the flame, which is underneath, and by the bath.

The equipment for carrying into effect the afore-mentioned method is characterized by the fact that it has at least two conduits, which are suitably arranged and separately movable, the first for the purpose of conveying the fuel and the second for conveying the fuel and the second for coinveyin the oxygen, both being equipped with means of regulation.

The aforementioned equipment is also characterized by the fact that it has:

At least three conduits, arranged one on the other, and being separately movable; the first and the second for the purpose of conveying the gaseous fuel or fuels, the liquid fuel or fuels, and the bottommost one for the purpose of conveying the oxygen, all of them being equipped with means of regulation;

A burner which is movable in the vertical and horizontal planes, and containing three or more pipes arranged on superposed planes; the top ones for the purpose of conveying the gaseous fuels or fuel and the liquid fuel or fuels; the bottom one for the purpose of conveying the oxygen; they are all equipped with means of regulation and are protected by an empty space through which a cooling fluid flows;

The terminal portion of the nozzle conveying the oxygen being equipped with a convergent-divergent nozzle functioning as a diffuser for the purpose of transforming, at the end of the flow, a very high pressure there available so as to increase its velocity which, in the minimum section of the piping already reaches the velocity of sound;

A pipe for the central feeding of solid, liquid or gaseous substances, which enters the pipe which carries the oxygen and which has a flow orifice which is arranged so as to correspond to the minimum section of the nozzle in such a way that the said substances are carried to the centre of the jet of oxygen and carried along by same;

At least two pipes for the peripheral supply of solid, liquid or gaseous substances which make their way obliquely into the pipe which supplies the oxygen, and having flow orifices which connect with the nozzles divergent surface; in such a way that the substances are carried to the outside of the jet of oxygen carried along by the latter.

The invention will now be further described with reference to the accompanying drawings which illustrate, in diagrammatic form and solely for the purpose of example, a piece of equipment in accordance with the invention, two particularities of the nOZZle prefitted on the oxygen flow orifice, and one application of the equipment. In these drawings:

FIG. 1 is the longitudinal section of a burner,

FIGURES 2 and 3 are longitudinal sections of two types of convergent-divergent nozzle to be fitted so that they communicate with the end of the oxygen flow and designed for the introduction of substances into the actual jet,

FIG. 4 is vertical section of an end of the open hearth.

furnace, with a burner fitted.

As regards FIGURE 1, reference 1 denotes the outer body of the burner, the outer surface of which is in contact with the combustions hot gases, and the inner surface of which is Washed by the cooling Water; 2 is the inner body of the burner, the outer and inner surfaces of which are washed by the cooling water; 3 is the space which subsists between the outer body 1 and the inner body 2 and which forms the empty space between the two bodies inside which the cooling water flows; 4 is the pipe for the gaseous fuel which is built into the top portion of the inner body 2; 5 is the regulating valve for the gaseous fuel, and 6 is the gases flow end fitted on the head of the outer body 1; 7 is the pipe for the liquid fuel, which is built into the inner body 2, below the pipe 4; 8 is the regulating valve for the liquid fuel, and is the liquid fuels flow end fitted on the head of the outer body 1; i0 is the oxygen pipe, which is built into the inner body 2, below the pipe 7; at the end 12 of the pipe 7 is fitted a convergent piping 13 and divergent piping 14, acting as a nozzle fitted on the head of the outer body 11; ll is the valve for regulating the oxygen;

15 is the bottom closure of the outer end of the body 2 which is traversed by the three pipes 4, 7 and 10; 16 is the connection for the intake of the cooling water which is connected to the outer portion of the inner body 2, and 1'7 is the connection for the cooling water outlet, which is connected to the outer portion of the outer body 1.

As regards FIGURES 2 and 3, reference 18 denotes the oxygen feed pipe which terminates at 12; 19 is the convergent-divergent piping, or nozzle, fitted at the end of the pipe 13; Si is the intake section, Sc is the critical section, and St is the end section of the nozzle 19; 20 is the pipe for the central supply of solid, liquid or gaseous substances, which enters the pipe 10, having the flow orifice 21 communicating with the critical section Sc of the nozzle 19 and located on the axis of this same nozzle; 22 are the two pipes for the peripheral supply of solid, liquid or gaseous substances which enter the nozzle 19 obliquely and have flow orifices 23 communicating with the divergent surface 14.

As regards FIGURE 4, reference 24 is the head of an open hearth furnace; 25 is the sole of the said furnace, and 26 is the vaulted roof of the same furnace; 27 is the upper level of the bath; 28 shows the highest position, and 29 the lowest position which may be assumed by the axis of the burner; 30 are the two generatrixes of the cone formed by the lighted fuel, and 31 are the two generatrixcs of the cone formed by the oxgen; 32 is the axis about which the burner turns on the vertical plane; the arrows indicate the path followed by the air which is pre-heated by the regenerator.

The manner in which the equipment functions is as follows: The jet of the ignited liquid fuels, with the jets of the gaseous fuels, forms a flame which is substantially in the shape of a cone; below the said fiame the oxygen is distributed at a velocity exceeding that of sound, the said oxygen, as it emerges from the nozzle 19 also forming a jet which is substantially in the shape of a cone, the upper portion of which enters the cone of ignited fuels located above, whilst the lower portion of the jet of oxygen reaches the charge.

If, by means of the regulating valves being adjusted singly or jointly, the supply of fuel and oxygen is varied, it will be possible to obtain automatically the interference required by the cone of oxygen with that of the flame, and the action of the oxygen on the charge.

Distributed in this manner, the oxygen, by combined action (mass, velocity and oxidation) acts on the flame, the charge, and on their heat exchange. In particular, the oxygen improves the fiames characteristics, accelerates, first of all, the fusion, and then the transformation of the charge, and it acts direct on the molten metal after first having removed from the latter the layer of slag floating on top.

Moreover, the oxygen succeeds in burning, near the bath, the gases which are set up by the latter, producing a better yield from the operation and preventing the combustion of the said gases from spreading to places where it would be of no value for the operation as such and indeed dangerous for the refractory lining. With this better distribution of oxygen there is obtained a more uniform action on the charge without excessive concentrations of heat and without the consequent development of red iron oxide fumes.

Using the equipment which is the subject of the present invention it is possible to distribute appropriately quantitics of 2500 Nmc./h. of oxygen (with an average consumption of Nrnc./t.) resulting in a doubling of the production (average hourly production 60 t./h. in an open hearth furnace with a capacity of 250 tons) at a smaller prime cost and lower specific consumption of fuel and refractories.

In FIGURE 4 is shown, for the purpose of example, the mounting of a burner in accordance with the invention on one of the two heads of an open hearth furnace, though the mounting is made on the two heads with the aim of utilising the air which has been pre-heated again by the regenerator; the operation of the two burners takes place consecutively and alternately.

The burner in accordance with the invention may also be used with any other type of open hearth furnace and with any other type of charge and fuel. The pipe which Nmeznormal cubic meter.

conducts the oxygen may also be fitted separate from the burner in cases where an independent movement on the part of the burner is desired.

With the convergent-divergent pipings of the kind shown in FIGURES 2 and 3 it is possible to introduce, into the jet of oxygen, solid, liquid or gaseous substances such as are suitable for the performance of the siderurgical operation or for the protection of the fireproof lining.

The said substances come in respectively either centrally or peripherally, in suitable positions, for the purpose of being swept along in the jet of oxygen while remaining, respectively, in the desired zone, be it central or peripheral.

Depending on the requirements of the particular siderurgical operation, use will be made, for example, of the following substances: iron alloys, coal, deoxidizers, lime,

water, steam, inert gases, etc.

Although, for descriptive reasons, the present invention has been illustrated on the basis of what has previously been described, many modifications and variations may be made in the execution of the equipment, particularly as regards: the structure of the divergent portion of the nozzle for the oxygen, the reciprocal position of the pipes which carry the fuels, the positions and structure of the flow orifices of the substances which are injected into the jet of oxygen, all these modifications and variations being nevertheless based on the fundamental ideas of the invention as summarized in the following claims.

What we claim is:

1. Apparatus adapted for the intensive utilization of oxygen in an open-hearth furnace for the production of steel comprising, in combination with said furnace, a device for supplying gaseous fuel, liquid fuel and oxygen simultaneously to said furnace, said device having a first conduit for connection to a supply of said gaseous fuel, a second conduit for connection to a supply of said liquid fuel disposed below said first conduit, and a third conduit for connection to a supply of said oxygen, said second conduit and said third conduit being effective to introduce said ignited fuel and said oxygen in the form of cone shaped jets with the upper portion of the cone-shaped jet of oxygen intercepting the lower portion of the coneshaped jet of ignited fuel, and said third conduit being effective to supply said oxygen at high velocity including the speed of sound and speed above the speed of sound, said third conduit having a discharge end defining a convergent-divergent passageway for said oxygen, said device being pivotaily mounted in said furnace for selectively directing said fuel and said oxygen in said furnace, and means for regulating flow through each of said conduits.

2. Apparatus adapted for the intensive utilization of oxygen in an open-hearth furnace for the production of steel comprising, in combination with said furnace, a device for supplying gaseous fuel, liquid fuel and oxygen simultaneously to said furnace, said device having a first conduit for connection to a supply of said gaseous fuel, a second conduit for connection to a supply of said liquid fuel disposed below said first conduit, and a third conduit for connection to a supply of said oxygen, said second conduit and said third conduit being effective to introduce said ignited fuel and said oxygen in the form of coneshaped jets with the upper portion of the cone-shaped jet of oxygen intercepting the lower portion of the coneshaped jet of ignited fuel, and said third conduit being effective to supply said oxygen at high velocity including the speed of sound and speed above the speed of sound, but said third conduit having a discharge end defining a convergent'divergcnt passageway for said oxygen, said device being pivotaliy mounted in said furnace for selectively directing said fuel and said oxygen in said furnace, and means for regulating fiow through each of said conduits, said device being movable in vertical and horizontal planes and being provided with a surrounding jacket for receiving a circulating cooling medium.

3. Apparatus adapted for the intensive utilization of oxygen in an open-hearth furnace for the production of steel comprising, in combination with said furnace, a device for supplying gaseous fuel, liquid fuel and oxygen simultaneously to said furnace, said device having a first conduit for connection to a supply of said gaseous fuel, a second conduit for connection to a supply of said liquid fuel disposed below said first conduit, and a third conduit for connection to a supply of said oxygen, said device being pivotally mounted in said furnace for selectively directing said fuel and said oxygen in said furnace, said second conduit and said third conduit being effective to introduce said ignited fuel and said oxygen in the form of cone-shaped jets with the upper portion of the cone-shaped jett of oxygen intercepting the lower portion of the coneshaped jet of ignited fuel, and said third conduit being effective to supply said oxygen at high velocity including the speed of sound and speed above the speed of sound, and means for regulating flow through each of said conduits, the terminal outlet portion of said third conduit being provided with a convergent-divergent nozzle which acts as a diffuser for the purpose of transforming, at the end of the oxygen flow, the very high pressure there available into an increase in flow velocity which, in the minimum section of the conduit, reaches said speed of sound.

4. Apparatus adapted for the intensive utilization of oxygen in an open-hearth furnace for the production of steel comprising, in combination with said furnace, a device for supplying gaseous fuel, liquid fuel and oxygen simultaneously to said furnace, said device having a first conduit for connection to a supply of said gaseous fuel, a second conduit for connection to a supply of said liquid fuel disposed below said first conduit, and a third conduit for connection to a supply of said oxygen, said second conduit and said third conduit being effective to introduce said ignited fuel and said oxygen in the form of coneshaped jets with the upper portion of the cone-shaped jet of oxygen intercepting the lower portion of the coneshaped jet of ignited fuel, and said third conduit being effective to supply said oxygen at high velocity including the speed of sound and speed above the speed of sound, said third conduit having a discharge end defining a convergent-divergent passageway for said oxygen, said device being pivotally mounted in said furnace for selectively directing said fuel and said oxygen in said furnace, and means for regulating flow through each of said conduits, said third conduit being provided axially with an inlet pipe for the axial supply of soild, liquid and gaseous substances, said pipe having its outlet orifice positioned to communicate with the portion of the third conduit of minimum diameter whereby said substances are carried to the center of the oxygen jet and are swept along by the latter.

5. Apparatus adapted for the intensive utilization of oxygen in an open-hearth furnace for the production of steel comprising, in combination with said furnace, a device for supplying gaseous fuel, liquid fuel and oxygen simultaneously to said furnace, said device having a first conduit for connection to a supply of said gaseous fuel, a second conduit for connection to a supply of said liquid fuel disposed below said first conduit, and a third conduit for connection to a supply of said oxygen, said second conduit and said third conduit being effective to introduce said ignited fuel and said oxygen in the form of cone-shaped jets with the upper portion of the cone-shaped jet of oxygen intercepting the lower portion of the coneshaped jet of ignited fuel, said device being pivotally mounted in said furnace for selectively directing said fuel and said oxygen in said furnace, and means for regulating flow through each of said conduits, said third conduit being provided with a convergent-divergent nozzle which acts as a diffuser for the purpose of transforming, at the end of the oxygen flow, the very high pressure there available into an increase in flow velocity which, in the minimum section of the conduit reaches said speed of sound, and said third nozzle being provided with at least two pipes for the peripheral supply of solid, liquid and gaseous substances obliquely into the oxygen supply conduit, said pipes having out-let orifices communicating with the divergent surface of the third conduit whereby the substances are carried towards the outside of the jet of oxygen and swept along by the latter.

References Cited in the file of this patent UNITED STATES PATENTS 1,513,828 Kernohan et al. Nov. 4, 1924 1,983,927 Bent et al. Dec. 11, 1934 2,039,087 Kinzel Apr. 28, 1936 2,362,085 Morgan Nov. 7, 1944 2,484,272 Crowe Oct. 11, 1949 2,550,848 Moody May 1, 1951 2,554,609 Barnes et al May 29, 1951 2,669,511 Whitney Feb. 16, 1954 2,878,115 Schane et a1. Mar. 17, 1959 FOREIGN PATENTS 556,732 Belguim May 13, 1957 OTHER REFERENCES Corsi'ni: Industrial Heating, July 1948, pp. 1174 and 1176 only. 

1. APPARATUS ADAPTED FOR THE INTENSIVE UTILIZATION OF OXYGEN IN AN OPEN-HEARTH FURNACE FOR THE PRODUCTION OF STEEL COMPRISING, IN COMBINATION WITH SAID FURNACE, A DE- 